1. Field of the Invention
The present invention relates to a wire fixing jig for fixing a plurality of covered wires when a circuit is formed by causing the plurality of covered wires to intersect with each other and then welding the wires at points of intersection.
The present application is based on Japanese patent Application No. 2000-387633, which is incorporated herein by reference.
2. Description of Related Art
When a circuit is formed by connecting a plurality of electrical conductors to one another, the electrical conductors are sometimes made to intersect with one another. Then, intersection portions of the electrical conductors are welded to one another by ultrasonic welding. In this case, the electrical conductors are fixed by a wire fixing jig in such a manner as not to shift when the ultrasonic welding is performed.
A conventional wire fixing jig is described in JP-A-9-29445. As shown in FIG. 5, this conventional wire fixing jig 13 has a plate-like fixing jig body 3, on which the electrical conductors 1 are arranged. The jig 13 is further provided with a plurality of accommodating grooves 5, which are formed in the jig body 3, and a plurality of through holes 7 formed therein respectively corresponding to the points of intersection of the accommodating grooves 5.
The accommodating grooves 5 are provided in a grating-like manner in the top surface portion of the fixing jig body 3. When arranged on the fixing jig body 3, the electrical conductors 1 are respectively accommodated in the accommodating grooves 5 thereby to be fixed to the fixing jig body 3.
Further, the through holes 7 are formed at the points of intersection of the accommodating grooves 5 arranged in a grating-like manner, respectively, and each penetrate the fixing jig body 3 from the top surface thereof to the bottom surface thereof. As shown in FIG. 6, each of these through holes 7 permits a pair of horns 11, which serve as welding device for welding intersection portions of electrical conductors 1 arranged in a grating-like manner on the fixing jig body 3, to penetrate therethrough. Further, the inner peripheral surface of each of the through holes 7 has a diameter that is nearly equal to or slightly larger than the diameter of the outer peripheral surface of each of the pair of horns 11.
When the electrical conductors 1 are connected to one another by using such a wire fixing jig 13, first, the electrical conductors 1 are accommodated in the accommodating grooves 5, and the conductors 1 are fixed to the fixing jig body 3 in such a way as to be arranged in a grating-like manner. Subsequently, intersection portions 9 of the electrical conductors 1 fixed to and arranged on the fixing jig body 3 in a grating-like manner are ultrasonic-welded by the pair of horns 11. At that time, the pair of horns 11 are set so that the diameter of the outer peripheral surface of each of the horns 11 is nearly equal to the diameter of the outer peripheral surface of each of the electrical conductors 1.
When the intersection portions 9 of the electrical conductors 1 are ultrasonic-welded, the intersection portions 9 and the pair of horns 11 are mutually positioned, as illustrated in FIG. 6. During this state, the pair of horns 11 are introduced into a corresponding one of the through holes 7 (not shown) from above and below, respectively. Thus, each of the intersection portions 9 of the plurality of electrical conductors 1 is held between a corresponding pair of the electrical conductors 1.
Then, when each of the intersection portions 9 is ultrasonic-vibrated by the corresponding pair of horns 11 during pressurized therebetween, opposed end portions of the horns 11 are crushed by the corresponding intersection portion 9, and thus spread in the direction of width thereof, so that the contact area of each of the end portions increases, and that the end portions are welded to each other.
When a plurality of covered wires are ultrasonic-welded by using the wire fixing jig 13, the wires are first accommodated in the accommodating grooves 5 and then fixed to the fixing jig body 3 in a grating-like manner, and ultrasonic-vibrated by simultaneously pressurizing intersection portions of the covered wires by means of the horns 11, similarly as in the case of ultrasonic-welding the electrical conductors 1.
When the covered wires are ultrasonic-vibrated by simultaneously pressurizing the intersection portions of the covered wires by means of the horns 11, the cover portions of the plurality of covered wires, which are in contact with one another at the intersection portions thereof, and the cover portions of the plurality of covered wires, which are in contact with the horns 11, are melted by ultrasonic vibration performed by the horns 11. At that time, the cover portions melted owing to pressurization performed by the horns 11 are extruded outwardly. Moreover, core parts of the wires come into contact with each other in a state in which these core parts are spread in the direction of width thereof.
Then, when ultrasonic vibration is performed on the intersection portions by the horns 11 during the intersection portions are pressurized, the core parts of the intersection portions of the plurality of covered wires, which are in contact with each other, are welded to each other.
However, in the case of the conventional wire fixing jig 13, each of the electrical conductors 1 is nearly equal in diameter to each of the horns 11. Each of the through holes 7 is formed in such a way as to have a diameter that is approximately equal to or slightly larger than the diameter of each of the horns 11. Therefore, the diameter of each of the through holes 7 is almost equal to or slightly larger than that of each of the electrical conductors 1. Thus, a space formed between the periphery of each of the intersection portions 9 and the inner peripheral surface of a corresponding one of the through holes 7 is small in a state in which the of electrical conductors 1 are arranged on the fixing jig body 3.
Thus, in the case of using the wire fixing jig 13 for connecting the covered wires, when the cover portions melted owing to the ultrasonic vibration performed by the horns 11 are extruded by being pressurized by means of the horns 11, there is a fear that the inner peripheral surface of the through hole 7 restrains the extrusion of the melted cover portions, and that the core parts are thus restrained from being spread in the direction of width thereof.
Hence, the wire fixing jig 13 has encountered problems that the core parts of the intersection portions of the covered wires are insufficiently electrically conducted in a state in which the core parts are welded to each other, and that the connection among the covered wires is electrically unstable.
Conversely, when the space formed between the peripheral surface of the corresponding one of the intersection portions and the inner peripheral surface of the corresponding one of the through holes 7 is enlarged by making the diameter of each of the through holes 7 larger than the diameter of the corresponding covered wire, the diameter of each of the through holes 7 becomes large in comparison with that of each of the corresponding horns 11. Thus, there is a fear that the entire fixing jig body 3 is shifted with respect to the horns 11 when the intersection portions are pressurized and ultrasonic-vibrated by the horns 11, and in that state, in which the positioning of the intersection portions and the horns 11 is performed, is canceled.
Consequently, in the wire fixing jig 13, the welding of the core parts at the intersections of the covered wires cannot be reliably performed. Thus, sometimes, the connection between the intersection portions is electrically unstabilized.
Furthermore, when not only the diameters of the thorough holes 7 but the diameters of the horns 11 are set in such a way as to be larger than the diameters of the covered wires, there is a fear that the size of the entire welding device increases.
An object of the invention is to provide a wire fixing jig enabled to electrically stably connect covered wires and to prevent the size of welding device from increasing.
To achieve the foregoing object, according to the invention, there is provided a wire fixing jig (hereinafter referred to as a first wire fixing jig) for arranging a plurality of covered wires each having a core part, which is constituted by a plurality of electrical conductors and insulated by being coated with a cover portion, in such a way as to intersect with a corresponding one of the remaining covered wires and for fixing the plurality of covered wires by being used when intersection portions are welded by simultaneously being pressurized by welding device so as to form a predetermined circuit. The wire fixing jig comprises a plate-like fixing jig body on which the plurality of covered wires are arranged, a plurality of supporting portions, which are formed at least around the intersection portions to be welded, each for supporting a corresponding one of the plurality of covered wires at positions, of which are located at predetermined pitches from a corresponding one of the intersection portions, at both sides in a longitudinal direction thereof and for ensuring a space that allows a core part of each of the intersection portions, which are pressurized when welded, to spread out, and through holes, which are provided in the fixing jig body correspondingly to the intersection portions of the plurality of covered wires placed on the fixing jig body and adapted so that the welding device is inserted into and penetrates through each of the through holes when the intersection portions of the plurality of covered wires are welded to each other.
According to the first fixing jig of such a configuration, a plurality of covered wires are arranged on the fixing jig body so that each of the covered wires intersects with a corresponding one of the remaining covered wires. Further, each of the covered wires is supported by the corresponding supporting portions around the corresponding intersection portion, which is welded, at positions, each of which is located at a predetermined pitch from a corresponding one of the intersection portions, at both sides in the longitudinal direction of each of the covered wires. At that time, a space is ensured by the corresponding supporting portions around the corresponding one of the intersection portions that are welded.
When each of the welding device pressurizes and welds the corresponding one of the intersection portions of the covered wires during this state, each of the spaces, which is ensured around the corresponding intersection portion, allows the corresponding intersection portion to spread out in the direction of width of the corresponding core part.
According to another embodiment (hereinafter referred to as a second wire fixing jig) of the invention, the supporting portions comprise pairs of columnar elements provided on the fixing jig body in such a way as to project therefrom so that the columnar elements of each of the pairs are opposed to each other. Further, the covered wires are supported by opposed portions, which are opposed to each other, of the columnar elements of each of the pairs in a state in which the covered wires are placed on the fixing jig body.
According to the second wire fixing jig of the invention, when the covered wires are placed on the wire fixing body so that each of the covered wires intersects with a corresponding one of the remaining covered wires, each of the covered wires is supported by the corresponding pair of columnar elements of the supporting portions.
Another embodiment (hereinafter referred to as a third wire fixing jig) of the invention further comprises a plurality of insulating columnar portions provided on the fixing jig body at predetermined pitches so that the insulating columnar portions and the supporting portions insulate the welded intersection portions of the covered wires.
According to the third wire fixing jig of the invention, the welded intersection portions adjoining the covered wires are insulated by the insulating columnar elements and the supporting portions.
An embodiment (hereinafter referred to as a fourth wire fixing jig) of the third wire fixing jig of the invention further comprises a lid, which is securely fixed to an end portion of each of the insulating columnar portions, for closing a side, at which the covered wires are place, of the fixing jig body.
According to the fourth wire fixing jig of the invention, each of the welded intersection portions is insulated from the exterior by closing the side, on which the covered wires are placed, of the fixing jig body with the lid.